Open Science Grid (OSG) and LHC Computing Grid (LCG) are two grid infrastructures that were built independently on top of a Virtual Data Toolkit (VDT) core. Due to the
demands of the LHC Virtual Organizations (VOs), it has become necessary to ensure that these grids interoperate so that the experiments can seamlessly use them as one
resource. This paper describes the work that was necessary to achieve interoperability and the challenges that were faced. Problems overcome and solutions are discussed along with a recommendation on what are the critical components
required for retaining interoperabilty. The current state of the interoperations actively is described, an outline for the future direction.